Reverse Words in a String ?

Problem statement

Let a string representing a sentence. A sentence is composed of words separated by a space. For example: "Welcome to Algo Planet" is a sentence. To make easier, we do not consider cases where words are separated by several spaces.
The goal is to find a solution in-place which reverses the sentence word by word. With our previous example, the solution must return "Planet Algo to Welcome".

Take a paper and a pen anf find the solution !